Spun bonded nonwoven webs having autogenous spot bonds are described in U.S. Pat. No. 3,855,046, Hansen et al. U.S. Pat. No. 3,949,128 illustrates elastic spun bonded nonwovens having spot bonds arranged in a pattern which is elongated and distorted in response to forces exerted in the machine direction causing the filaments to buckle between the spot bonds with subsequent heat setting. Stretchability in the cross direction may be achieved by a later microcreping process. An increase in basis weight is caused by such bulking. U.S. Pat. No. 4,374,888 illustrates a non-woven laminate including exterior layers of spun bonded nonwoven webs each having autogenous bonds arranged in widely dispersed patterns of spot bonds in side by side relation and in rows both in the machine direction and in the cross direction and having an intermediate melt blown layer. These layers are pattern bonded utilizing a sonic horn.
It is an important object of this invention to provide a spun bonded nonwoven web which has been stretched to provide a soft "hand" and greater coverage with minimal sacrifices in strength as a result of stretching in either the machine direction or in the cross direction although there is a substantial reduction in basis weight of the web commensurate with the amount of dimensional increases.
Another important object of the invention is the provision of a spun bonded nonwoven web having a symmetrical pattern of autogenous spot bonds arranged in such a way as to provide marginal "secondary bonding" from which portions of continuous filament become disengaged when the web is subjected to stress in the machine direction or in the cross direction prior to release of the filaments in the spot bond.
Still another object of this invention is to increase the stretchability of a spun bonded nonwoven web having spot bonds arranged in a pattern conducive to symmetrical displacement upon the application of stress in the machine direction or in the cross direction.